Unmanned Systems Technology 014 | Quantum Tron | Radio links and telemetry | Unmanned Aerial Vehicles | Protonex fuel cell | Ancillary systems | AUVSI 2017 Show report

43 as we’re flying it on small UAVs at 30- 100 m over the water, the data collected is of an incredibly high resolution.”           The hyperspectral sensor was developed at the IFE’s Research Engineering Facility, and Prof Gonzalez and his team are developing software to quickly analyse the hyperspectral information from the reef, as well as detect invasive plants in Western Australia and diseases in wheat crops and vineyards. The engineers also developed and built a lightweight gimbal that enables stabilised image capture from the camera on board QUT’s UAV. This can survey 40 hectares of the reef in 30 minutes at 100 m, which gives a spatial resolution of approximately 15 cm per pixel – much higher than the 7.5 m resolution possible from high- altitude craft. “The hyperspectral camera allows for the classification of corals, sand and algae based on their unique spectral signatures,” Prof Gonzalez says. “We’re now building AI algorithms that can automatically recognise and classify these signatures – the hyperspectral equivalent of a police ‘fingerprint database’. “This database will become increasing valuable to environmental researchers in the future. “There are many advantages to using smaller hyperspectral cameras and a UAV. It’s flexible and quick to deploy, as a mission can be scheduled any time in strategic locations where a higher level of detail is required,” he says. Agriculture US agricultural UAV start-up Sentera takes a flexible approach to endurance. Its sensors can be fitted onto its own fixed-wing craft or a commercial rotary UAV, depending on the needs of the application. For high-endurance applications though it has developed a low-cost fixed-wing UAV. The 1.8 kg Phoenix has variants to support precision agriculture, mapping and public safety industries, and is hand-launched. It has a flight time of up to an hour at 35 mph, covering up to 700 acres during a mission. The autopilot constantly auto-calculates the grid pattern specified by the user to ensure the most efficient and therefore quickest data collection. That is a key requirement, according to Todd Colten, Sentera’s chief aerospace engineer. He says, “Agronomists, crop consultants and growers fly their fields repeatedly during a growing season, looking for comparative data. The Phoenix can be programmed to fly exactly the same pattern many times, ensuring data comparability.” Live digital video allows the operator to monitor the ground from the sky in real time. Sentera has also been working on reducing the size and weight of its range of sensors. It is developing a double 4K sensor for the Phoenix that provides true RGB and normalised difference vegetation index (NDVI) data in a single flight. The ground sampling distance is less than 1.5 in per pixel at a flying height of 400 ft, and the sensor payloads are specifically designed for UAV applications by having automatic geotagging of all images with millisecond precision. That means no geotagging post-processing is needed, which allows faster data analysis. The same tagging is used in Sentera’s quad sensor, a multispectral imager with red-edge capabilities that is also used for monitoring and assessing the quality of crops. Sentera offers a high-precision single sensor as well, in two variants – NDVI and normalised difference red edge (NDRE). “Targeted data capture allows users to filter out ‘spectral noise’ and collect only the isolated emissions in the red, red-edge, and NIR bands that are true indicators of crop health,” says Sentera’s chief mechanical engineer Ryan Nelson. “That means that what the sensor identifies as red, red-edge or NIR content is in the proper spectral region. “With many cameras currently on the market you’ll see a lot of overlap between colour channels, which affects the accuracy of the vegetative health index. When developing our high-precision agriculture sensor line, we implemented filtering techniques that provide precise spectral data with complete band separation, so users can always collect accurate and reliable NDVI or NDRE measurements.” Fixed-wing UAV developer PrecisionHawk is also working on UAVs | Insight Unmanned Systems Technology | June/July 2017 Sentera has focused on a lightweight, hand-launched fixed-wing UAV to provide longer flight times for agricultural monitoring (Courtesy of Sentera)